A Conditional Access Module (CAM) card is a digital video module used for connecting a television set and an external signal source. The CAM card can convert compressed digital signals to television content and display the television content on the television set. The CAM card and a smart card are used cooperatively and inserted into an integrated digital television with a Common Interface (CI), so that a user can directly watch the ordered digital television content without a set top box.
The CAM versions before version CI/CI+1.3 only supported the input and output of a single data stream. In other words, only one transfer stream could enter the CAM card and then be outputted to the host from the CAM card after being processed in the CAM card.